Fluid operated switch



June

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INVENTORSSA4 JoHN R. OT-ro BY HERBERT A, PlDcocK ATTORNEY United StatesPatent Office Patented June 10, 1969 3,449,535 FLUID OPERATED SWITC HJohn R. Otto, St. Louis, and Herbert A. Pid'cock, Maplewood, Mo.,assignors to EssexfhlI/Ianufacturing C0., Inc., Gravois Mo. acorporation o ssoun FiiedAug. 1, 1966, ser. No. 569,296

Int. Cl. H01h 35/38 U.S. Cl. 200-82 10 Claims ABSTRACT F THE DISCLOSUREThis invention relates in general to pressure sensitive devices and,more particularly, to a switch adapted for operating responsively to apressure differential in fluid systems.

It is an objective of the present invention to provide a switch adaptedfor circuit controlling operation responsive to pressure differential ina fluid system, wherein the media may be liquid or gaseous, such asespecially encountered in aerospace fluid systems. u

It is another object of the present invention to provide a switch of thetype stated which incorporates hermetically sealed pressure sensingelements for precluding contact between the fluid media and actuatingmechanisms or electrical elements of the switch, thereby conducing tothe long effective life of the switch, as Well as eliminating anypotential danger when the fluid medium is hazardous.

It is another object of the present invention to provide a switch of thecharacter stated incorporating pressure sensing elements which inmovement responsive to applied uid pressure are substantiallyfrictionless so as to thereby obviate any possible explosions or tiresby reason of ignition of the fluid medium through sparks.

It is a further object of the present invention to provide a Huidoperated switch which is of extreme sensitivity so that a pressuredifferential in the order of one l) pound per square inch will operatethe switch.

It s a further object of the present invention to provide a switch ofthe character stated which incorporates means for Iadjusting same forpredetermined pressure settings, as well as to prevent overtravel ofswitch actuating components.

It is a still further object of the present invention to provide adevice which may be readily adapted for a multiplicity of purposes, suchas for use to sense the pressure drop across a restriction in the pathof flow of the fluid; or to serve as a proportional indicator, apotentiometer, etc.

It is a still further object of the present invention to provide a fluidoperated switch which is economical in construction, efiicient andreliable in operation; which is free from delicate components so as tobe capable of withstanding continued, heavy usage.

`Other objects and details of the present invention will be apparentfrom the following description when read in connection with theaccompanying drawing (two (2) sheets), wherein FIGURE 1 is a top planview of a fluid operated switch constructed in accordance with andembodying the present invention.

FIGURE 2 is a front elevational view.

FIGURE 3 is a vertical transverse sectional view taken on the line 3-3of FIGURE l.

FIGURE 4 is an end elevational view in partial section, taken on theright hand side of FIGURE 1.

FIGURE 5 is a horizontal transverse sectional view, taken on the line5-5 of FIGURE 2.

FIGURE 6 is a vertical transverse sectional view taken substantially onthe line 3 3 of FIGURE 1 but illustrating another form of fluid operatedswitch constructed in accordance with and embodying the presentinvention.

Referring now by reference characters to the drawings which illustratepractical embodiments of the present invention, A generally designates afluid operated switch, comprising a body 1 formed from a four-sidedblock, having a bore 2 extending throughout its length from its upper toits lower end 3, 4, respectively.

Secured upon the said upper end and lower end, as by screws s, are upperand lower end plates 4, 6, respectively, which are integrally providedwith axially aligned conduit ttings 7, 8, respectively, forcommunication with bore 2. Formed on the inwardly presented surfaces ofsaid plates 5, 6, are relatively shallow, inwardly projecting rings orannuli 9, 10, respectively, having an outside diameter substantiallyequivalent to the diameter of bore 2, for projection thereinto with theouter surfaces of said rings 9, 10 abutting the adjacent confrontinginner face portion of bore 2.

Said bore 2, together ywith end plates 5, 6, co-operate to define achamber 11, within which is received a plunger 12 for axial reciprocal,slideable movement therein, being of free-floating character. Saidplunger 12 is of circular cross-section and of general H-shape invertical section (see FIGURE 3) in that the Same integrally comprises acentral transverse partition 137 and endwise opening compartments 14, 15on either side thereof; the latter being delimited by the adjacent faceof partition 13, and the proximate side wall portions of said plunger12. Said plunger 12 is of a length less than the distance between theend faces of opposed rings 9, 10 of plates 5, 6 which rings serve -asstops for limiting the travel of plunger 12 within chamber 11. Thethickness of rings 9, 10 is substantially the same as that of the sidewall portions of compartments 14, 15.

Disposed within each of the compartments a pressure sensing element 16,17, respectivel which comprises a bellows assembly; at their inner endagainst the adjacent confronting face of partition 13 of plunger 12, andat their outer ends `abutting against the inner faces of the related endplates 5, 6. Each bellows assembly 16, 17 is in communication with theproximate conduit fitting 7, 8, respectively, and are hermeticallysealed so that fluid received therein is denied contact with anyelements of the switch thereby preventing malfunction of the switchthrough undesired contact with the liuid media. i

Bellows assemblies 16, 17 are extremely sensitive to pressure, so thatthe same are longitudinally expansible, or travel, under applied uidpressure, causing resultant axial movement of plunger 12, within chamber11, dependent upon the relative Huid pressure within said bellowsassemblies 16, 17. As shown in FIGURE 3, the pressures within the saidbellows assemblies 16, 17 are equal so that plunger 12 is in centeredrelationship, being equidistant from the detent surfaces of rings 9, 10.Overtravel of the bellows 16, 17 in both directions is prevented byabutment of plunger 12 against either ring 9, 10, so that the saidbellows 16, 17, are protected against such potential damage.

Formed in the outer surface of the partition portion of plunger 12 isagroove 18, which registers with a relatively 14, 15 is y, each of saidlatter abutting enlarged opening 19 in the adjacent wall portion of body1 through which latter projects the curvate, hook-forming, free end of aswitch actuator 20 formed preferably from riait spring stock. Saidactuator 20 at its opposite end is mounted upon a pin 21 projecting fromthe leg 22 of an 'angle bracket 23, the other leg 24 of which is mountedupon the outer adjacent surface of body 1 (see FIGURES 4, Leg 24 ofbracket 23 is provided with a vertically extending slot-like aperture25, for allowing vertical adjustment of said bracket 23, with respect tothe retaining bolts 26, 26 extending therethrough.

Also mounted, as by screws 27', upon leg 22 of angle bracket 23 is `amicro-switch 27, having the conventional actuating button 28 which atits outer end is immediately adjacent the central, relatively linearportion of actuator 20. Bracket 23 together with micro-switch 27 andactuator 20 carried thereon is enclosed by a housing 29 maintained inposition lby bolts 30 which are threaded- 1y engaged within openings 31,tapped in the proximate portion of body 1 (see FIGURE 5). Micro-switch27 is connected to the related electrical system or circuit (not shownor forming a part of the present invention) as by leads 32, 33, 34,which -are led outwardly of housing 29 through an opening therein (notshown) carrying a grommet 35.

The free end of actuator 20 is curved on a radius for normalcomplementary reception within groove 18 o-f plunger 12 and thorugh thebias of the mounting of said actuator, the same will be normally urgedinto said groove 18. With the plunger 12 in balanced position, whereinthe pressures exerted thereon by bellows 16, 17 are equal, actuator 20will be urged into groove 18, and hence away from actuating button 28 ofmicro-switch 27. Upon the development of a relatively greater pressurein either bellows assemblies 16, 17 so as to cause travel of saidplunger 12 in a direction away from the bellows assembly having thegreater pressure, a camming action will develop between the hooked orcurvate end of actuator 20, and the wall portions of plunger 12 adjacentgroove 18 so as to force said actuator 20 against its normal bias as itleaves groove 18 thereby applying a force against actuating button 28 ofmicro-switch 27 for tripping of the latter. When the iiuid pressure inthe system returns to a balanced state, the plunger 12 will be returnedto centered position, with the curvate end of actuator 20 being restoredto groove 18, with release of switch-tripping contact with actuatingbutton 28.

In view of the foregoing, a normal differential of the pressures withinsensing elements 16, 17 will effect travel or floating of plunger 12 soas to bring about switch tripping action. It is obvious that switch 27may be so set as to be closed or opened by the movement of plunger 12.The extreme sensitivity of bellows assembles 16, 17 to the pressure ofthe received fluids whether the same be liquid or gaseous, will allowfor switch action upon development of small differentials, such as inthe order of one (l) pound per square inch. Since said sensing elements16, 17 are hermetically sealed, all the operating parts of device A areprotected `against damage contact with fluids which may in manyinstances be `quite hazardous as well as restrictive of the componentelements.

In View of the foregoing, it is apparent that switch A is peculiarlyadapted for reliable functioning over a long life and having asensitivity to differential of pressures Within ai fluid pressure systemso as to be adaptable for utilization in a multiplicity of industrialapplications.

'It is quite obvious that switch A may be modified for myriad purposes,such as for instance by `setting one of the two bellows assemblies 16,17 at a fixed absolute pressure, so that with the other bellows assemblybeing yadapted for expansion, the system could be used as a aneroid orabsolute pressure sensor. With the said pressure sensors as provided bysaid bellows assemblies 16, 17, it is apparent the present inventioncould be readily designed for use as a proportional indicating device, apotentiometer, as a liow indicator and the like. It is further manifestthat if plunger 12 were replaced by a piston, the bellows assemblies 16,17 would render the resultant structure capable of serving as a valvewhich could shut off, restrict or proportionally divide tluid flow.

Bellows assemblies 16, 17 are adaptable for use with diiferent fittingsand with a variety of mounting conligurations. Fittings 7, 8 which areadapted for use with tubing by other types of well-known fittings may beused with equal effectiveness.

Another feature of the present invention is the adjustability of salmesince the desired positioning of angle bracket 23 will permit ofpre-determined pressure settings by reason of movement of the actuatorand micro-switch assembly longitudinally. By means of a slot 36 formedin leg 22 of ybracket 23, pin 21 may be adjusted for preventingactuating button 28 from being overtraveled due to tolerance built up ofthe various parts.

With reference being made to FIGURE 6, A' generally designates a fluidoperated switch which is substantially similar to fluid switch A abovedescribed in that the same incorporates a body 1', communicating withconduit fittings 7', 8', at its opposite ends and internally having achamber 11' for slideably receiving therein a plunger 12' being ofgeneral H-shape with a central partition 13' and endwise openingcompartments 14', 15' for receiving pressure sensing elements 16', 17',each of which comprises a bellows assembly; there being a groove 18'formed in the outer face of partition 13'; all of said components andelements being of like construction as the corresponding components andelements of fluid operated switch A described hereinabove. The wallportion of body 1 is provided with an enlarged opening 40 whichregisters with groove 18 of partition 13 for extension therethrough of acylindrical actuator 41 having a rounded outer end for projection intosaid groove 18 and for camming relationship with the marginal portionsthereof; said actuator 41 being disposed for axially slideable movementwithin an annular socket 42 carried upon a bracket 43 suitably mountedupon outer face of the proximate portion of body 1'; said bracket 43being substantially structurally identical with bracket 23 abovedescribed. Bracket 43 mounts a micro-switch 27' having an actuatingbutton 28' which said switch and button are identical with switch 27 andbutton 28 described hereinabove. Said button 28' projects into the saidsocket 42 for normal abutment against the inner end face of actuator 41.

Thus, upon axial movement of plunger 12' within chamber 11' pursuant topressure differentials between the said bellows assemblies 16', 17',camming engagement will develop between the marginal portions of groove18 and the rounded outer end of actuator 41 so as to cause same to moveinwardly, or in a direction toward microswitch 27', thereby forcingbutton 28 inwardly and bringing about the desired operation ofmicro-switch 27'. Upon return of plunger 12 to centered position withinchamber 11', actuator 41 will be thereby released for outward movementinto the position shown in FIGURE 6 which will be effected by release ofthe normal bias upon actuator button 28', resulting in the prearrangedoperation of micro-switch 27.

It will be seen that switch A incorporates a cylindrical, bullet-likeactuator which is slideably movable along its longitudinal axis andrestrained against non-axial movement by socket 42. Thus, reliable andconstant action will be assured.

It should be understood that changes and modications in formation,construction, and arrangement and combination of the several parts ofthe Huid operated switch may be made and substituted for these hereinshown and described without departing from the nature and principle ofour invention.

We claim:

1. A tiuid operated switch comprising:

(a) means defining a housing;

(b) a plunger slideably received within said housing for reciprocaltravel therein and having a pair of compartments;

(c) fluid pressure sensitive means disposed in each of said compartmentsfor effecting sliding movement of said plunger;

(d) a circuit switch disposed adjacent said housing;

and

(e) switch actuator means engaged to said switch and connected to saidplunger for operatively interengaging said switch and said plunger fortripping of the former upon movement of the latter.

2. A uid operated switch as dened in claim 1, and

further characterized by:

(b) said plunger being of general H-shape in crosssection, having acentral partition portion and a compartment on either side of saidpartition, each of said compartments opening through the adjacent end ofsaid plunger; and

(c) said fluid pressure sensitive means being disposed in each of saidplunger compartments;

(f) a source of fluid; and

(g) means connecting said source of fluid to the fluid pressuresensitive means in each of said plunger compartments.

3. A fluid operated switch as dened in claim 2, and

further characterized by:

(c) said fluid pressure sensitive means comprising bellows assembliesdisposed in each of said plunger compartments, each assembly engagingthe adjacent confronting face of said central partition.

4. A fluid operated switch as defined in claim 3, and

further characterized by:

(b) said plunger being of less length than the said housing; and

(h) stop means provided in said housing for limiting the travel of theplunger therein.

5. A uid operated switch as defined in claim 4, and

further characterized by:

(i) said housing having end plates;

(h) said stop means comprising an annulus integrally formed on the innerface of each end plate; and

(b) said plunger being of circular cross-section.

6. A fluid operated switch as defined in claim 2, and

being further characterized by:

(a) said housing having an opening in one side portion thereof;

(d) said switch being disposed adjacent said housing opening;

(e) said switch actuator means comprising an arm projecting through saidhousing opening for engaging said plunger and being presented inoperative relationship to said switch; and

(j) means for mounting said arm.

7. A fluid operated switch as defined in claim 6, and

further characterized by:

(b) said plunger having a groove provided in its outer surfacesubstantially intermediate its length in normal registration with saidhousing opening; and

(e) said switch actuator arm havin-g a curvate portion for normaldisposition within said groove for camming action with said plunger upontravel thereof for effecting switch operation.

8. A uid operated switchas dened in claim 7, and

further characterized by:

(j) said switch actuator arm being resiliently mounted for being biasedinto engaged relationship at its curvature end wtihin said plungergroove; and

(d) said circuit switch having a control button presented proximate saidswitch actuator arm for operative engagement thereby upon travel of saidplunger.

9. A uid operated switch as delined in `claim 8, and

further characterized by:

(k) means for adjusting the setting of said switch and actuator arm`with respect to said plunger.

10. A fluid operatetd switch as dened in claim 2 and furthercharacterized by:

(e) said switch actuator means comprising a cylindrical member;

(l) means defining a support for said switch actuator for slideablelmovement thereof.

References Cited UNITED STATES PATENTS 7/ 1956 Stevenson 200-82 7/1965Andersen 20G-83

